@article{SM_1989_64_2_a12,
     author = {A. A. Davydov},
     title = {Singularities of fields of limiting directios of two-dimensional control systems},
     journal = {Sbornik. Mathematics},
     pages = {471--493},
     publisher = {mathdoc},
     volume = {64},
     number = {2},
     year = {1989},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1989_64_2_a12/}
}